High-pressure FTIR Research Articles

Features of Wax Appearance Temperature Determination of Waxy Crude Oil Using Attenuated Total Reflection Fourier Transform Infrared Spectroscopy Under Ambient and High Pressure.

The wax appearance temperature (WAT), being one of the key characteristics of waxy crude oil and other waxy substances, is used for the necessary assessment of the phase stability of materials during various technological processes. However, the determination of this parameter as well as peculiarities of wax formation under high gas pressure suffers from the lack of suitable techniques for this task. To address this issue, an attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR) method has been applied for the first time to measure the WAT of waxy crude oil under high gas pressure. Carbon dioxide (CO2), nitrogen, and natural gas were used in the study due to their widespread applicability as injection gases in enhanced oil recovery methods. The S2/S1 versus temperature method based on changes in the band of rocking vibrations of the CH2 group was applied to determine WAT. It was found that the ATR FT-IR method based on the proposed dependence S2/S1 versus temperature gives lower WAT values compared to those observed by viscometry, magnetic resonance imaging inspection, and cross-polarized microscopy methods for the waxy crude oil studied. A detailed analysis was carried out using variable-temperature ATR FT-IR spectra of waxy crude oil in the temperature region near the WAT. Essentially different dynamics of wax crystal formation in waxy oil sample and model paraffin solution were demonstrated during the cooling process. The results obtained by high-pressure ATR FT-IR showed that CO2 and natural gas reduce the WAT, while nitrogen has virtually no effect. In addition, for the studied oil, it was found that high pressure of CO2 and natural gases leads to a visual decrease in the amount of wax crystals precipitated, but not to the complete disappearance of microcrystals at a certain temperature and pressure. The results obtained proved that ATR FT-IR can be an effective method for proper determinations of WAT under high-pressure conditions similar to those met in practice.

Efficient and stable tripodal Phosphine-Controlled Pd-Catalyst for anti-Markovnikov hydroaminocarbonylation of alkenes with aromatic amines

The tripodal phosphine [L1, 1,1,1-tris(diphenylphosphino-methyl)ethane] was applied to control the activity, regioselectivity, and stability of the involved Pd-catalyst in anti-Markovnikov hydroaminocarbonylation of alkenes with aromatic amines for the synthesis of linear-amides. Due to the unique characters of L1 in terms of the steric bulkiness, the switching-coordination mode from tripodal phosphine to bidental one, and the robustness against moisture and oxygen, L1 conferred to Pd-catalyst with the high activity, good regioselectivity, and excellent stability for this carbonylation, leading to 44 ∼ 87 % yields of the target amides with L/B of greater than 80/20. The in situ high-pressure FT-IR analysis and the DFT calculations verified that L1 not only promoted the formation and stability of PdII-H active species (ν ca. 1932 cm−1) but also facilitated the anti-Markovnikov’s addition of alkenes with PdII-H bond due to the favorable energy level of linear intermediate (B-1). In addition, since L1 can coordinate to Pd(II)-center as a bidental chelator as fulfill catalysis and then coordinate to Pd(0)-center as an tripodal pincer, Pd-catalyst was protected timely by L1 against metal-deposition (Pd0-black precipitation) to guarantee its stability for recycling uses for 5 runs without activity loss.

Can CO2 be a catalyst? Yes, CO2-catalyzed N-formylation of aliphatic amines with DMF

Carbon dioxide (CO2) was found to serve as a novel and green catalyst for the first time in N-formylation of amines with N, N-dimethylformamide (DMF), wherein only the aliphatic amines were applicable to afford the formamides in the yield of 71∼95%. The isotope labeling experiment with DMF-d7 indicated that the N-formyl group in the formylated product was originated from DMF rather than CO2. The control experiments and the in situ high-pressure FT-IR spectra demonstrated that the formation of the carbamate salt of cyclohexylammonium cyclohexylcarbamate (A) derived from the reaction of CO2 with cyclohexylamine was the driving force for this reaction. Accordingly, the mechanism of CO2-catalyed N-formylation of aliphatic amines with DMF was proposed, involving the formation of carbamate salt intermediate with enhanced nucleophilicity in anion in favor of the attack on carbonyl-group of DMF.

Efficient hydroaminomethylation of olefins catalyzed by Rh-complex ligated by P,O-hybrid ligand with chelating effect

Tandem hydroaminomethylation (HAM) represents one of the most important catalytic protocols for the one-pot synthesis of amines using low-cost and widely available olefins, syngas and amines as starting materials. In this work, the applied P,O-hybrid ligand containing phosphino-fragment and carboxylic group [L1, 2-(diphenylphosphino)benzoic acid] could stoichiometrically react with Rh(acac)(CO)2 to afford a stable Rh-complex of Z [dicarbonyl-2-(diphenylphosphino)benzoato rhodium(I)], wherein the more substantial P,O-chelation derived from L1 as a bidental pincer upon deprotonation as well as the thermodynamically favored six-membered ring structure warranted its stability. It was found that Z could serve as a highly active catalyst to accelerate the reaction rate of each individual step in the HAM, advantageous with the completely inhibited side-reaction of olefin-hydrogenation. The in situ high-pressure FT-IR spectral analysis demonstrated, for the first time, that the involvement of L1 greatly facilitated the formation of two kinds of the active Rh-H intermediates (A′ and A, v 2012 and 2043 cm−1) with well-maintained longevity. And the DFT calculations further confirmed that the Rh-complex of Z exhibited exclusive ability to activate H2, resulting in the efficient formation of Rh-H intermediates of A′ and A, the later (A) was responsible for rapid olefin-hydroformylation, and the former (A′) was in charge of imine-hydrogenation.

BIO-UTILIZATION OF INDUSTRIAL WASTE: CHARACTERIZATION AND ANTIOXIDANT ACTIVITY

Peels, seeds, liquids, and molasses are among the waste products produced by the fruit and vegetable processing industries. These waste products are rich in carbohydrates, proteins, fibers, vitamins, and minerals. Fermentation can be used to produce colors from this waste. Our trash disposal concerns are solved and pollution in the environment is reduced by reusing these materials. Solid-state fermentation of Blakeslea transport (+) MTCC 884 was used. Orange, carrot, and papaya peel waste can be used to mine and optimize environmental elements for the formation of carotene. All factors had a significant impact on -carotene production, with a determined yield of 0.125-0.128 mg/mL. A variety of techniques were used to characterize the extracted color, including High-Pressure Liquid Chromatography (HPLC), LC-MS, mass spectroscopy, and FTIR. (Rt 13.37) was confirmed by mass spectroscopy of the extracted color, which yielded 537.608 as the mass/charge ratio (m/z). A further 76 percent of these fruits and vegetable wastes contained -carotene, suggesting that they could be used to produce pure carotene. DPPH and ABTS tests indicate that it has good antioxidant capabilities. Keywords: Fruit Peel Waste, Fermentation, HPLC, FTIR, UV-V

Co-Catalysis for Hydroamidocarbonylation of Alkynes with Amides over a Bifunctional Ligand-Based Pd Catalyst.

The hydroamidocarbonylation of alkynes with amides allows for the synthesis of α,β-unsaturated imides with the advantage of 100% atomic economy. Herein, the bifunctional ligand (L1) containing a sulfonic acid group (-SO3 H) and phosphino-fragment enable the Pd catalyst to accomplish the hydroamidocarbonylation of alkynes with amides. It was found that, due to an intramolecular synergetic effect, the L1-based Pd-catalyst exhibited much higher activity than the individual mechanical mixtures of Xantphos-based Pd-complex and MeSO3 H. The formation and stability of Pd-H species were promoted by the presence of L1, which was verified by in situ high-pressure FT-IR analysis. Under the optimized conditions, the target products of the branched imides were obtained with yields in the range of 46-87% over the L1-based Pd-catalyst. Advantageously, as an ionic ligand, the L1-based Pd-catalyst could be recycled for 4 runs in the ionic liquid of [Bmim]NTf2 without any obvious activity loss and detectable metal leaching.

On the extraordinary pressure stability of the Thermotoga maritima arginine binding protein and its folded fragments - a high-pressure FTIR spectroscopy study.

The arginine binding protein from T. maritima (ArgBP) exhibits several distinctive biophysical and structural properties. Here we show that ArgBP is also endowed with a ramarkable pressure stability as it undergoes minor structural changes only, even at 10 kbar. A similar stability is also observed for its folded fragments (truncated monomer and individual domains). A survey of literature data on the pressure stability of proteins highlights the uncommon behavior of ArgBP.

Pd-catalyzed alkoxycarbonylation of alkenes promoted by H2O free of auxiliary acid additive

The Pd-catalyzed alkoxycarbonylation of alkenes using water as a promoter has been scarcely reported before. Herein, water instead of Brønsted/Lewis acid was found to effectively improve the catalytic performance of Pd(MeCN)2Cl2-Xantphos system for alkoxycarbonylation of alkenes. Under the optimal conditions, the best yield of 97% was obtained for the target products (methyl 3-phenylpropanoate and methyl 2-phenylpropanoate) with L/B of 4.3 and TON of 192. With the involvement of water, Pd(MeCN)2Cl2-Xantphos system also exhibited the moderate to good generality to alkoxycarbonylation of different kinds of alkenes with alcohols. The in situ high pressure FT-IR analysis verified that water played an important role in promoting formation and stability of PdH active species which was responsible for the efficient alkoxycarbonylation of alkenes. In addition, the ligand effect of Xantphos on this reaction was discussed.

Enhanced Selectivity of Phenol Hydrogenation in Low-Pressure CO2 over Supported Pd Catalysts

Selective hydrogenation of phenol to cyclohexanone is an important process in both chemical industry and renewable feedstock processing. However, direct hydrogenation of phenol to cyclohexanone under mild conditions over catalysts with high reactivity, selectivity, and facile preparation is still a challenge. In the present study, we report that 99% conversion and 99% selectivity can be achieved over as-prepared Pd/γ-Al2O3 catalyst under the medium of low-pressure CO2 (0.05–0.2 MPa) and H2O at 373 K. According to experiment results, ab initio calculations and in situ high-pressure FTIR measurements indicated enhanced selectivity of cyclohexanone in low-pressure CO2; this result originated from the molecular interaction between cyclohexanone and CO2 and can prevent the further hydrogenation of cyclohexanone. Notably, enhancement of selectivity to cyclohexanone in low-pressure CO2 was also achieved using commercial Pd/γ-Al2O3 and Pd/C catalysts.

Probing Conformational and Functional Substates of Calmodulin by High-Pressure FTIR

In response to intracellular Ca2+-concentration changes, the highly dynamic and flexible Ca2+-sensing protein calmodulin (CaM) interacts with more than 300 diverse target proteins that are involved in numerous signaling pathways in eukaryotic cells. This unique promiscuous target binding behavior and the underlying functional versatility of CaM is a result of its structural flexibility. CaM spans multiple conformational substates in solution providing adaptable binding surfaces for different target proteins. K-Ras4B, known as a key regulator in the ERK pathway, was identified as specific binding partner of CaM, causing the dissociation of the lipidated K-Ras4B from the plasma membrane and thus reducing its activity. However, the interaction of K-Ras4B and CaM has not been elucidated in detail until now. In order to evaluate the conformational space of CaM and shed more light on the mechanism of subsequent target recognition and protein function, identification and characterization of functionally relevant conformational substates is mandatory. Applying pressure in combination with spectroscopies such as FTIR spectroscopy enables to populate and probe otherwise transient low-lying excited conformational substates of CaM close in energy to ground state, but with a smaller partial volume. Evidence has grown that these states are functionally relevant, for instance in recognition and ligand binding events. The pressure-induced conformational changes of CaM were studied in its Ca2+-free and Ca2+-bound state and in the presence of the C-terminal K-Ras4B peptide. We show that not only Ca2+-binding, but also the presence of the target peptide has a drastic effect on the conformational dynamics of the protein.

Probing conformational and functional substates of calmodulin by high pressure FTIR spectroscopy: influence of Ca2+ binding and the hypervariable region of K-Ras4B.

The ubiquitous Ca2+-sensing protein calmodulin (CaM) interacts with more than 300 diverse target proteins that are involved in numerous signaling pathways in eukaryotic cells. This unique promiscuous target binding behavior and the underlying functional versatility of CaM is a result of its structural flexibility. CaM spans multiple conformational substates in solution providing adaptable binding surfaces for different target proteins. The conformational space of this protein needs to be explored to shed more light on the mechanism of target recognition and protein function. Here, we used pressure modulation in combination with FTIR spectroscopy to populate and probe otherwise transient low-lying excited conformational substates of CaM close in energy to its ground state, which are supposed to be functionally relevant in recognition and ligand binding events. The pressure-induced conformational changes of CaM were studied in its Ca2+-free and Ca2+-bound state and in the presence of the hypervariable region (HVR) of the signaling peptide K-Ras4B as a binding partner. We demonstrate that the conformational dynamics of CaM is vastly affected by binding of both Ca2+ ions and the lipidated signaling peptide K-Ras4B. Moreover, we could uncover conformational substates of CaM by pressure perturbation that are partially unfolded and more solvated and conceivably facilitate target recognition by exposing the required binding surfaces.

Immobilization of a rhodium catalyst using a diphosphine-functionalized ionic liquid in RTIL for the efficient and recyclable biphasic hydroformylation of 1-octene.

A highly efficient and stable Rh-P catalytic system in the RTIL of [PEmim]BF4 was developed for the biphasic hydroformylation of 1-octene by using the diphosphine-functionalized ionic liquid (FIL) of 2. While 2-Rh(acac)(CO)2 was immobilized in [PEmim]BF4 (solvent), a typical biphasic catalysis was fulfilled with advantages of facile separation and recycling ability - 9 runs without any loss of activity. It was found that not only the acquired π-acceptor character of 2, but also the synergetic role of the piperidyl group in [PEmim]BF4 as an N-containing donor, cooperatively contributed to the efficient hydroformylation due to the facilitated formation and stability of the Rh-H active species (ν 2045 cm(-1)). This was supported by the in situ high-pressure FT-IR spectral analysis.

Promotion effect of water on hydroformylation of styrene and its derivatives with presence of amphiphilic zwitterionic phosphines

Two kinds of novel zwitterionic phosphines of L1 and L2 have been synthesized in which the sulfonate groups (–SO3–) are incorporated to render them amphiphilic. Both of them are strong π-acceptor ligands in which the positive-charged imidazoliums with intensive electron-withdrawing effect are vicinal to the coordinating phosphorous atoms. The amino-group of piperidyl is additionally incorporated in L2 to make it behave as a hybrid ligand with potential hemilability. The comparison of the ligands of L1 and L2 in Rh-catalyzed hydroformylation of styrene (and its derivatives) and the effect of water on their behaviors were discussed. Without the involvement of water, the catalytic system of Rh(acac)(CO)2-L2 exhibited lower activity than that of Rh(acac)(CO)2-L1 under the same conditions. However, the dramatic promotion effect of water as a suspension was observed especially for Rh(acac)(CO)2-L2 system with TOF spurred up from 195 to 470h−1. The corresponding in situ high pressure FT-IR spectral information showed that the presence of water in Rh(acac)(CO)2-L2 system greatly facilitated the formation and stability of the active Rh–H species (νRh-H, 2047cm−1), which was in charge of the efficient hydroformylation of styrene and its derivatives.

In situ investigation of supercritical CO2 assisted impregnation of drugs into a polymer by high pressure FTIR micro-spectroscopy.

An original experimental set-up combining a FTIR micro-spectrometer with a high pressure cell has been built in order to analyze in situ the impregnation of a solute into microscopic polymer samples, such as fibers or films, subjected to supercritical CO2. Thanks to this experimental set-up, key factors governing the impregnation process can be simultaneously followed such as the swelling of the polymeric matrix, the CO2 sorption, the kinetics of impregnation and the drug loading into the matrix. Moreover, the solute/polymer interactions and the speciation of the solute can be analyzed. We have monitored in situ the impregnation of aspirin and ketoprofen into PEO (Polyethylene Oxide) platelets at T = 40 °C and P = 5; 10 and 15 MPa. The kinetics of impregnation of aspirin was quicker than the one of ketoprofen and the final drug loading was also higher in the case of aspirin. Whereas the CO2 sorption and the PEO swelling remain constant when PEO is just subjected to CO2 under isobaric conditions, we noticed that both parameters can increase while the drug impregnates PEO. Coupling these results with DSC measurements, we underlined the plasticizing effect of the drug that also leads to a decrease in the crystallinity of PEO in situ thus favoring the sorption of CO2 molecules into the matrix and the swelling of the matrix. The plasticizing effect increases with the drug loading. Finally, the speciation of drugs was investigated considering the shift of the carboxyl bands of the drugs. Both drugs were found to be mainly homogeneously dispersed into PEO.

Ionic Rh(I)-complexes containing π-accepting and hemilabile P,N-ligands as efficient catalysts for hydroformylation of 1-octene

The ionic hybrid P,N-ligands of 1 and 2 have been synthesized as one type of unconventional tertiary phosphines with the advantages of both the π-accepting ligands and the hemilabile ligands. The corresponding ionic Rh(I)-complexes of 1A and 2A proved to be more efficient catalysts for hydroformylation of 1-octene over isomerization than the traditional RhI(acac)(CO)(PPh3), due to the π-backdonation interaction in Rh→P linkage and the hemilabile ligation of N,P-coordinating sites to Rh-center. The in situ high-pressure FT-IR analysis indicated that: (1) the formation and lifetime of the active RhH species (2047cm−1) derived from 1A are facilitated by the presence of ligand 1; (2) the formation of the active RhH species is depressed without the aid of the P,N-hemilabile ligation; and (3) the active RhH species derived from RhI(acac)(CO)(PPh3) is unstable and susceptible to the formation of the inactive carbonyl-bridged Rh-dimer.

A high-temperature, ambient-pressure ultra-dry operando reactor cell for Fourier-transform infrared spectroscopy.

The construction of a newly designed high-temperature, high-pressure FT-IR reaction cell for ultra-dry in situ and operando operation is reported. The reaction cell itself as well as the sample holder is fully made of quartz glass, with no hot metal or ceramic parts in the vicinity of the high-temperature zone. Special emphasis was put on chemically absolute water-free and inert experimental conditions, which includes reaction cell and gas-feeding lines. Operation and spectroscopy up to 1273 K is possible, as well as pressures up to ambient conditions. The reaction cell exhibits a very easy and variable construction and can be adjusted to any available FT-IR spectrometer. Its particular strength lies in its possibility to access and study samples under very demanding experimental conditions. This includes studies at very high temperatures, e.g., for solid-oxide fuel cell research or studies where the water content of the reaction mixtures must be exactly adjusted. The latter includes all adsorption studies on oxide surfaces, where the hydroxylation degree is of paramount importance. The capability of the reaction cell will be demonstrated for two selected examples where information and in due course a correlation to other methods can only be achieved using the presented setup.

Multiphase reaction media including dense phase carbon dioxide and/or water: A case study for hydrogenation of phenol with a Pd/Al2O3 catalyst

Multiphase reaction media including dense phase CO2 and/or water were applied for a test reaction of hydrogenation of phenol with a Pd/Al2O3 catalyst. The features of these reaction media were clarified and the actions of dense phase CO2 and water were discussed. Different characterization methods (XPS, in situ high pressure FTIR, ICP) were used to study (i) the surface of supported Pd particles that varied during the reaction, (ii) the competitive adsorption of phenol, water, and CO that was formed from H2 and CO2 under pressurized conditions, and (iii) the leaching of active Pd species. Dense phase CO2 caused the deactivation of catalyst and it occurred more rapidly in the presence of both dense phase CO2 and water. In the system including water alone, the catalyst deactivation also happened but gradually. At the latter stage of reaction in this system, phenol was not consumed but cyclohexanone did transform to cyclohexanol. Those results may be explained by the leaching of Pd species and a structural change of supported Pd particles, resulting in a change in their adsorption behavior. The Pd leaching is more significant in acidic aqueous phase dissolving CO2 at high pressure.

Hydrous ringwoodite to 5 K and 35 GPa: Multiple hydrogen bonding sites resolved with FTIR spectroscopy

Multiple substitution mechanisms for hydrogen in γ-(Mg,Fe)2SiO4, ringwoodite, lead to broad, overlapping, and difficult-to-interpret FTIR spectra. Through combined low-temperature, high-pressure synchrotron-based FTIR spectroscopy, the multiple bonding sites become evident, and can be traced as a function of temperature and compression. Multiple OH stretching bands can be resolved in iron-bearing and iron-free samples with 0.79-2.5(3) wt% H2O below 200 K at ambient pressure, with cooling to 5 K at 35 and 23 GPa resulting in the resolution of possibly as many as 5 OH stretching bands traceable at room temperature from 23 GPa down to 8 GPa. A distribution of defect mechanisms between ‴Mg″+2(H·) at 3100, 3270, and possibly 2654 cm-1, ‴Si″′+4(H·) at 3640 cm-1, and MgSi″+2(H·) at 2800 cm-1 can then be resolved. These multiple defect mechanisms can therefore explain the higher electrical and proton conductivity in ringwoodite when compared to wadsleyite, and therefore may be applied to resolve spatial variations in water storage in the Earth’s transition zone.

A combined computational and experimental study of high pressure and supercritical CO2 adsorption on Basolite MOFs

Metal organic frameworks (such as commercial Basolite®) display significant promise for CO2 capture and storage. Here, in order to monitor CO2 capture of Basolite®, we combined high pressure CO2 adsorption with high-pressure FTIR and Monte Carlo simulations. We found that Basolite® C300 show an unprecedented rise in capture capacity above 25bars, as predicted by the DFT calculations. Adsorption isotherms were measured up to 200bar using a state-of-the-art magnetic suspension balance, and in-situ FTIR studies as a function of pressure allowed characterizing the preferential adsorption sites, and their occupancy with increasing pressure. Monte Carlo molecular simulations were used to infer nanoscopic information of the adsorption mechanism, showing the sorbent–CO2 interactions from structural and energetic viewpoints.

Behaviour of NTE Material Ag3[Co(CN)6] under Pressure

Recent discovery of colossal negative thermal expansion (NTE) behaviour in Silver Hexacyanocobaltate Ag3[Co(CN)6] has triggered interest among researchers to understand the basic mechanism causing such an unusual behaviour. This report presents our results on the behaviour of Ag3[Co(CN)6] using in-situ high pressure Raman and FTIR spectroscopy. The reported trigonal-monoclinic phase transition occurring in this compound is observed at 0.2 GPa. Upon increasing the pressure further, Ag3[Co(CN)6] becomes irreversibly amorphous above 13 GPa.